In a bid to prevent the spread of the polio virus in the Horn of Africa, Kenya, Ethiopia and Somalia will at the weekend embark on a simultaneous vaccination campaign targeting nearly three million children younger than five, the United Nations health agency said on Friday.

Somalia had been free of polio for three years until last year when cases of the paralysing disease, believed to have originated in Yemen, were detected. A total of 215 polio cases have been reported in Somalia since 2005, while neighbouring Ethiopia has reported 37 cases since December 2004, according to the World Health Organization (WHO).

Kenya has not reported any polio cases since 1984, but its proximity to the two countries has made vaccination necessary.

The three countries have large nomadic livestock-herding communities that often cross borders, raising the risk of the rapid spread of the polio virus. Their itinerant lifestyles also complicate effective vaccination efforts.

The 9-12 September synchronised vaccination campaign will be the largest such effort in the Horn of Africa, according to WHO. The campaign will involve religious and community leaders, women’s groups, youth associations, schools, and governmental and non-governmental organisations.

Polio is a highly infectious viral disease that mainly affects children younger than three. It affects the nervous system and can cause total paralysis in hours.